Custom CSS File Not Rendered in Blade View

I have some problems here. My View in Laravel Projects won't rendered the custom css but, it's only rendered the bootstrap.min.css by using bootstrap CDN in the layouts. Here is the code from the view that not get rendered :

@extends('layouts.app')

@section('banner')
<div class="position-relative overflow-hidden text-center bg-light">
    <!-- Carousel Headline -->
    <div id="carouselExampleIndicators" cl  ass="carousel slide" data-ride="carousel">
        <!-- Carousel Indicator -->
        <ol class="carousel-indicators">
            <li data-target="#carouselExampleIndicators" data-slide-to="0" class="active"></li>
            <li data-target="#carouselExampleIndicators" data-slide-to="1"></li>
            <li data-target="#carouselExampleIndicators" data-slide-to="2"></li>
        </ol>
    </div>
</div>
@endsection

In order to calling that view, i'm using controller like this :

    public function show($id)
    {
        $product = Product::find($id);
        return view('products.show')->with('product', $product);
    }

and this is my code in the layouts :

    <!-- Banner Part Start -->
    <section class="banner_part">
        <div class = "container">
            <div class="row align-items-center justify-content-center">
                <div class="col">
                    @yield('banner')
                </div>
            </div>
        </div>
    </section>

so anyone knows what's wrong in my codes?

via Chebli Mohamed